Identification guide · Sulfide Minerals
How to Identify Realgar
Realgar is usually red, orange-red, and orange with a resinous luster and is translucent. It has a Mohs hardness of 1.75. A fingernail (Mohs 2.5) scratches it easily. Its streak is orange-red to yellow-orange. It is most often confused with Orpiment, Vanadinite, and Amber; the tests below separate them.
Realgar identification checklist
| Color | Red, Orange-red, Orange | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Resinous | Compare a fresh surface with glass and metal; this luster is softer than either. |
| Transparency | Translucent | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 1.75 | A fingernail (Mohs 2.5) scratches it easily. |
| Streak | Orange-red to yellow-orange | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | Good | |
| Fracture | Conchoidal | Broken surfaces show smooth, curved, shell-like scoops. |
| Specific gravity | 3.56 | Heavier than it looks (specific gravity about 3.56). |
| Crystal system | Monoclinic |
Realgar look-alikes and how to tell them apart
Both sit near Mohs 1.75, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Realgar vs Orpiment →
Vanadinite is harder (Mohs 3) than Realgar (Mohs 1.75), so Vanadinite will scratch Realgar and not the other way round. A fingernail (Mohs 2.5) scratches it easily. Realgar vs Vanadinite →
Both sit near Mohs 1.75, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Realgar vs Amber →
Calcite is harder (Mohs 3) than Realgar (Mohs 1.75), so Calcite will scratch Realgar and not the other way round. A fingernail (Mohs 2.5) scratches it easily.
Field tips
- Look for a brilliant orange-red to red color, resinous luster, and an orange-red streak.
- Realgar is very soft and translucent, and old specimens may show a dusty yellow alteration crust.
- It commonly occurs with yellow orpiment in low-temperature veins, which helps confirm identification.
Realgar identification FAQ
How can you tell if a rock is Realgar?
Check the color (red, orange-red, and orange), the resinous luster, a Mohs hardness of 1.75 and a orange-red to yellow-orange streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Realgar?
Realgar has a Mohs hardness of 1.75. A fingernail (Mohs 2.5) scratches it easily.
What is the difference between Realgar and Orpiment?
Realgar (Mohs 1.75, resinous luster) and Orpiment (Mohs 1.75, resinous luster) look alike, but hardness, streak and heft usually separate them. See the full Realgar vs Orpiment comparison for a side-by-side table.
Is Realgar worth anything?
Entry-level Realgar specimens sell for around $10, typical collector pieces about $70, and premium examples $450 or more depending on size, quality and locality.
What color is Realgar?
Realgar is most often red, orange-red, and orange. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
